EXCHANGE 


8o6i 

"A"N 


Ammonium   Phospho-molybdate 


THESIS 


PRESENTED  TO    THE    FACULTY  OF  THE    GRADUATE    SCHOOL 

OF  THE  UNIVERSITY  OF  PENNSYLVANIA  IN  PARTIAL 

FULFILMENT  OF  THE  REQUIREMENTS  FOR  THE 

DEGREE  OF    DOCTOR  OF  PHILOSOPHY 


BY  V 

CHARLES  MCDOWELL  GILLAN,  B.S. 

PHILADELPHIA,  PA. 

1909 


PHILADELPHIA 

THE  JOHN  C.   WINSTON  CO 
1 910 


Ammonium   Phospho-molybdate 


THESIS 


PRESENTED  TO   THE   FACULTY  OF  THE   GRADUATE    SCHOOL 

OF  THE  UNIVERSITY  OF  PENNSYLVANIA  IN  PARTIAL 

FULFILMENT  OF  THE  REQUIREMENTS  FOR  THE 

DEGREE  OF    DOCTOR  OF  PHILOSOPHY 


BY 

CHARLES  MCDOWELL  GILLAN,  B.S. 

\\ 

PHILADELPHIA,  PA. 

1909  '»'!% 


PHILADELPHIA 

THE  JOHN  C.  WINSTON  CO. 

IQIO 


x  4 


ACKNOWLEDGMENT 

The  author  desires  to  express  his  gratitude  to  DR, 
EDGAR  F.  SMITH,  for  his  advice  and  encouragement  in  this 
•work,  which  was  undertaken  at  his  suggestion. 


AMMONIUM  PHOSPHO-MOLYBDATE. 
INTRODUCTION. 

This  salt  has  received  considerable  attention  from 
analysts.  The  results  of  the  investigations  upon  it  have  not 
been  altogether  satisfactory.  There  seems  to  be  quite  a  wide 
difference  in  the  ratios  existing  between  the  phosphoric  acid 
and  the  molybdic  acid.  Indeed  these  range  from  5 : 1 
upward  as  high  as  24:  I.  In  no  instance  has  the  cause  of 
this  remarkable  difference  been  definitely  determined. 

In  the  opinion  of  Wolcott  Gibbs1  the  formula  for 
ammonium  phospho-molybdate  is, 

24  Mo03.  P,05.  3(NH4)20  +  XH2O. 

Howrever,  in  the  course  of  his  investigation  there  was  dis- 
covered quite  a  large  series  of  salts;  these  he  classified  as 
follows : 

10  MoO3.  2  P2O5.  5(NH4)2O.  X  H2OXr=(;  or  20). 

10  MoO3.  2  P2O5.  6(NH4)2Q.  14  H2O 

32  MoOa.  2  P2O5.  6(NH4)2O.  28  H2O 

44  MoOa  2  P2Q5.  6(NH4)2O.  18  H2O 

48  MoO3.  2  P2Q5.  5(NH4)2O.  16  H2O 

22  MoOa.  i  P2O5.  3(NH4)2O.    9  H=O 

22  MoOs.  i  P2O5.  3(NH4)2O.  12  HSO 

60  MoO3  3  P2O5.  8(NH4)2O.  12  H2O 

16  MoO*.  i  PSO5.  3(NH4)2O.  14  H2O 

'In  this  study  he  was  disposed  to  assign  the  following 
general  formula  to  ammonium  phospho-molybdate: 

m  MoO3.  2P2O5.  n  R2O.  X  H2O. 

in  which  m  is  always  an  even  number,  varying  from  10  to 
48,  while  n  varies  from  3  to  6;  it  is  usually  6,  although  it 
aProc.  Am.  Acad.  Arts  and  Science,  17,   62. 

(3) 


444336 


may  exceed  that  number.  R  is  ammonium,  and  generally 
equals  6.  Wolcott  Gibbs  regarded  those  salts  as  normal  in 
which  there  were  six  ammonium  molecules,  the  salt  having 
a  ratio  of  60  :  3  or  practically  20  :  I  he  regarded  as  acci- 
dental, and  at  the  time,  felt  that  further  proof  was  necessary 
to  establish  its  existence.  This  proof  Debray2  supplied  later 
upon  analyzing  a  salt  which  gave  values  corresponding  to 
the  formula, 

20  MoO3.  P2O5.  3(NH4),O  +  3  H2O. 


That  the  ratio  20:1  was  correct,  Debray  felt  was  proved 
by  the  formula  of  the  following  silver  salt  : 

20  MoO3.  P2O5.  7  AgsO  +  24  H2O. 

Debray,  furthermore,  described  an  ammonium  salt  in 
which  the  ratio  of  molybdic  and  phosphoric  acid  was  5:1. 
His  analysis  of  this  salt  gave  the  formula, 

5  Mos.  P205.  3(NH4),0  +  7  H2O. 


In  addition  he  obtained  the  following  derivatives  : 

5  MoOs.  P205.  3  K20  +  7  H2O. 
5  MoOs.  P2O5.  3  Na*O  +  14  H2O. 
5  MoOs.  P2O5.  3  Ag£O  +  7  H2O. 

He  maintained  that  salts  of  the  higher  series  were 
decomposed  by  alkalies  and  passed  into  salts  where  the  ratio 
of  the  acids  was  5:1;  conversely,  that  the  addition  of  a 
mineral  acid  to  an  alkaline  solution  of  the  5  :  i  salt,  caused 
it  to  change  to  a  salt  of  a  higher  series. 

Debray's  study  on  ammonium  molybdate  in  which  the 
ratio  of  acids  was  5  :  I  was,  in  reality,  a  confirmation  of  the 
work  of  Zenker,3  who  had  previously  prepared  the  salt: 

5  MoOs.  P£OB.  3(NH4)2O+7  H2O. 

2Bull.  de  la  Soc.  Chim.  de  Paris  [2],   5^  404. 
3Fresenius'  Zeit.  fur  anal.  Chem.,  14,  12. 


Indeed,  Rammelsberg4  had  also  made  this  5 :  I  salt.  These 
results  are  highly  interesting  because  they  show  the  number 
of  molecules  of  molybdic  acid  to  be  uneven,  and  the  basicity 
of  the  complex  acid  seems  to  be  3  and  not  6.  To  the  neutral 
salt  Rammelsberg  assigned  this  formula: 

22  MoOa.  P2(X  3(NH4)tO.  12  H80. 

At  a  later  date,  Wolcott  Gibbs5  repeated  the  work  of 
Debray  and  was  able  to  confirm  the  results  obtained  by  the 
latter. 

Finkener,6  from  his  studies,  concluded  that  while  the 
percentage  of  water  and  ammonia  could  vary  within  wide 
limits,  the  ratio  between  the  molybdic  and  phosphoric  acids 
was  always  24:  i. 


EXPERIMENTAL. 

In  the  preparation  of  the  salts  later  analyzed  by  me, 
pure  ammonium  molybdate  was  dissolved  in  redistilled  am- 
monia, and  to  this  solution,  after  expelling  the  excess  of 
ammonia,  the  sodium  phosphate,  dissolved  in  a  definite  vol- 
ume of  water,  was  added.  The  mixture  of  the  two  solu- 
tions-was  then  boiled  for  one-half  hour  and  acidulated  with 
dilute  nitric  acid  (1:3).  The  precipitates  obtained  after 
this  fashion  were  uniform  in  color,  with  the  exception  of 
the  salts  number  6,  10  and  n. 

All  salts  analyzed  were  dried  to  constant  weight  at  a 
temperature  varying  between  no  and  120°. 

In  the  analysis  of  the  various  compounds  prepared  by 
me,  I  had  recourse  to  the  methods  which  were  suggested 
and  used  by  Wolcott  Gibbs  in  his  study  of  the  derivatives 

*Ber.,  10,  1776. 

5Proc.  Am.  Acad.  Arts  and  Science,  18,  232. 

cBer.,  10,   1638. 


of  the  complex  inorganic  acids.  As  these  methods  are 
familiar  to  analysts,  mere  reference  to  them  will  suffice.  The 
details  of  their  manipulation  will  be  found  amply  given  in 
the  original  papers  of  Gibbs. 

My  aim  was  to  ascertain,  with  a  knowledge  of  the  pre- 
ceding conflicting  data,  in  regard  to  the  constitution  of  com- 
mon phospho-molybdate,  just  what  would  result  upon  the 
use  of  the  three  sodium  salts  of  phosphoric  acid  with  definite 
amounts  of  molybdic  acid,  applied  in  the  form  of  ammonium 
molybdate,  under  definite  degrees  of  dilution.  Accordingly, 

SALT  No.  i 

was  prepared  by  bringing  together  12  grams  of  monosodium 
phosphate  and  14.4  grams  of  molybdic  acid.  This  mixture 
was  then  boiled  for  one-half  hour  and  acidulated  with  dilute 
nitric  acid  (1:3).  There  separated  the  usual  yellow  colored 
precipitate,  which  upon  analysis,  gave  these  results: 

.2068  grams  lost  .0191  grams  upon  ignition  =  9.23% 
.2117  grams  lost  .0196  grams  upon  ignition  =  9.28% 
.1923  grams  lost  .0176  grams  upon  ignition  =  9. 17% 
.2091  grams  lost  .0193  grams  upon  ignition  =  9. 


Mean  =  9.22% 

.2296  grams  gave  .2082  grams  mixed  oxides  =  90.68% 
.2016  grams  gave  .1829  grams  mixed  oxides  =  90.72% 
.2196  grams  gave  .1990  grams  mixed  oxides  =  90.62% 
.1914  grams  gave  .1644  grams  mixed  oxides  =  96.63% 


Mean  =  90.66% 

.;C2i6  grams  gave  .0132  grams  Mg2P2O7  =  379%  P2O5 
.2148  grams  gave  .0129  grams  Mg2P2OT  =  3.82%  P2O5 
.2063  grams  gave  .0123  grams  Mg2P2O7  =  3.83%  P2O5 
.1921  grams  gave  .0112  grams  Mg2P2OT  =  3.70%  P2O5 

Mean  =  3.78%  P2O5 


.20i6  grams  contained  .0078  grams  (NHOaO  =  3.87% 

.2114  grams  contained  .0079  grams  (NH4)2O  =  3.74% 

.1876  grams  contained  .0073  grams  (NH4)2O  =  3.69% 

.1812  grams  contained  .0069  grams  (NH4)2O  =  3.81% 

Mean  =  3.74% 

MoO3  by  difference   86.88% 

P205    378% 

(NH4)20    374% 

H2O  by  difference  5.48% 


Total    99-88% 

These  results  would  lead  to  the  formula: 
22  MoO3.  P2O5.  3(NH4)2O.   ii  H2O. 

SALT  No.  2. 

In  this  instance,  di-sodium  phosphate  was  substituted 
for  monosodium  phosphate.  The  quantities  of  material 
reacting  were  14.2  grams  of  di-sodium  phosphate  and  14.4 
grams  of  molybdic  acid  in  the  form  of  ammonium  molybdate. 
This  solution  was  treated  as  in  the  previous  case,  and  when 
tne  resulting  yellow  colored  precipitate  was  analyzed,  it  gave 
the  following  results : 

.2019  grams  lost  .0186  grams  upon  ignition  =  9.21% 

.2272  grams  lost  .0208  grams  upon  ignition  =  9.16% 

.2116  grams  lost  .0198  grams  upon  ignition  =  9.36% 

.1846  grams  lost  .0170  grams  upon  ignition  =  9.21% 


Mean  =  9.23% 

.2210  grams  gave  .2021  grams  of  mixed  oxides  =  91. 45% 
.1863  grams  gave  .1701  grams  of  mixed  oxides  =  91.30% 
.1921  grams  gave  .1754  grams  of  mixed  oxides  =  91.31% 
.2049  grams  gave  .1869  grams  of  mixed  oxides  =  91.22% 

Mean  =  91. 32% 


8 


.2060  grams  contained  .0075  grams  (NH4)2O  =  3.64% 
.2256  grams  contained  .0084  grams  (NH4)2O  =  3. 


Mean  =  3.68% 

.2145  grams  gave  .0127  grams  Mg2-P2O7  =  3.78%  P2O5 
•1939  grams  gave  .0116  grams  Mg2P2O-,  =  3.82%  P2OS 

Mean  =  3.80% 
MoO3  by  difference   ........................  87.50% 

P2O5    ......................................     7.80% 

(NH4)20    ..................................     3.68% 

H2O  by  difference    .........................     5-55% 


Total   ..................................  100.53% 

These  led  to  the  formula, 

22  MoO3.  P2O5.  3(NH4)2O.  ii  H2O. 

SALT  No.  3. 

Here  14.6  grams  of  tri-sodium  phosphate  were  boiled 
up  with  14.4  grams  of  molybdic  acid.  The  resulting  phos- 
pho-salt  analyzed  as  follows  : 

.2046  grams  lost  .0187  grams  upon  ignition  =  9.  14% 

.2023  grams  lost  .0188  grams  upon  ignition  =  9.28% 

.2097  grams   lost  .0194  grams  upon  ignition  =  9.25% 

.2084  grams  lost  .0191   grams  upon  ignition  =  9.16% 

Mean  =  9.21% 

.2039  grams  gave  .1850  grams  mixed  oxide  =  90.73% 
.2141  grams  gave  .1944  grams  mixed  oxide  =  90.85% 
.2026  grams  gave  .1837  grams  mixed  oxide  =  90.68% 
.2072  grams  gave  .1881  grams  mixed  oxide  =  90.78% 

Mean  =  90.76% 


.2043  grams  gave  .0113  grams  Mg2P2O7  =   . 
.2017  grams  gave  .0115  grams  Mg2P2Oi  =  3.62% 


Mean  =  3.57% 


.2ogi  grams  gave  .0068  grams  (NH4)2O  =  3-25% 

.2109  grams  gave  .0071  grams  (NH4)2O  =  3.37% 

.2014  grams  gave  .0065  grams  (NH4)  20  =  3.23% 

.2067  grams  gave  .0069  grams  (NH4)2O  =  3.34% 

Mean  =  3.29% 

MoO3  by  difference   £7.19% 

P,05    3-57% 

(NH4)2O    3-29% 

H,O  by  difference  5-92% 


Total    ..................................  99-97% 

From  these  percentages,  one  may  deduce  the  formula 
24  MoO8.  P2O5.  3(NH4)2O.  13  H.O. 


SALT  No.  4. 

The  quantities  of  reacting  substances  were  again 
changed  as  follows:  24  grams  of  monosodium  phosphate 
and  28.8  grams  of  molybdic  acid  were  brought  together  and 
treated  as  in  the  previous  examples.  The  product  of  the 
reaction,  when  submitted  to  analysis,  showed  these  results, 

.2072  grams   lost   .0195   grams  upon  ignition  =  9.41% 

.2013  grams  lost  .0190  grams  upon  ignition  =  9-44% 

.2057  grams  lost  .0192  grams  upon  ignition  =  9.33% 

.2091  grams  lost  .0197  grams  upon  ignition  =  9.42% 

Mean  =  9.40% 

.2119  grams  gave  .1920  grams  mixed  oxides  =  90.61% 
.2084  grams  gave  .1887  grams  mixed  oxides  =  90.55% 
.2106  grams  gave  .1906  grams  mixed  oxides  =  90.50% 
.2016  grams  gave  .1825  grams  mixed  oxides  =  90.53% 

Mean  =  90.55% 


.2039  grams  gave  .01  n  grams  Mg2P2O7  =  348  PaOs 
.2096  grams  gave  .0113  grams  Mg2P2O7  =  348  P2O5 
.2054  grams  gave  .01  n  grams  Mg2P2OT  =  346  P20s 


Mean  =  3.47  P2O5 


10 


.21 16  grams  gave  .0078  grams  (NH4)2O  =  3.69% 
.2047  grams  gave  .0073  grams  (NH4)2O  =  3.56% 
.1991  grams  gave  .0071  grams  (NH4)2O  =  3.57% 


Mean  =  3.61% 

MoO3  by  difference   87.08% 

P2O5    3-47% 

(NH4)20    3-61% 

H2O  by  difference  5-79% 


Total    99-95% 

From  which  there  is  deduced  the  formula, 
24  MoO3.   P2O5.  3(NH4)2O.  13  HaO. 

SALT  No.  5. 

Now  substituting  di-sodium  phosphate  and  allowing 
28.4  grams  of  it  to  react  with  28.8  grams  of  molybdic  acid, 
the  product  upon  analysis  showed: 

.2116  grams  lost  upon  ignition  .0230  grams  =  10.87% 
.2043  grams  lost  upon  ignition  .0221  grams  =  10.82% 
.2097  grams  lost  upon  ignition  .0226  grams  =  10.78% 
.2106  grams  lost  upon  ignition  .0230  grams  =10.92% 


Mean  =  10.85% 

.2031  grams  gave  .1807  grams  mixed  oxides  =  88.97% 
.1994  grams  gave  .1773  grams  mixed  oxides  =  88.92% 
.2097  grams  gave  .1867  grams  mixed  oxides  =  89.03% 
.2108  grams  gave  .1874  grams  mixed  oxides  =  88.90% 

,2041  grams  gave  .0133  grams  Mg2P2Or  =  4.i6%  P^Os 
.2079  grams  gave  .0134  grams  Mg2P2O7  =  4.i3%  P2O5 
.2011  grams  gave  .0131  grams  Mg2P2O7  =  4.i7%  P2O5 
.2092  grams  gave  .0134  grams  Mg2P2OT  =  4.n% 


Mean  =  4.14%  P2O5 


II 

.2io6  grams  gave  .0083  grams  (NH^O  =  3.94%  P2O5 

.2039  grams  gave  .0078  grams  (NH4)2O  =  3.83%  P2O0 

.2016  grams  gave  .0079  grams  (NHOaO  =  3.92%  P2O5 

.2009  grams  gave  .0076  grams  (NH4)2O  =  3.78%  P2O5 

Mean  =  378%  P2O5 


MoOs  by  difference   84.81% 

P2O5    4-14% 

(NH4)20    3.87% 

H,O  by  difference    6.98% 


Total    ..................................  99-8o% 

Here  the  deduced  formula  would  read, 

24,Mo03.   P205.  3(NH4)20.  13  H,O. 


SALT  No.  6. 

In  its  preparation  32.8  grams  of  tri-sodium  phosphate 
and  28.8  grams  of  molybdic  acid  were  boiled  together.  As 
tHe  resulting  yellow  colored  precipitate  showed  a  rather 
high  water  content  .upon  analysis,  portions  of  it  were  dried 
for  ten  hours  at  a  temperature  ranging  from  no  to  120°  C. 
This  drying,'  however,  apparently  made  no  change  in  the 
composition  of  the  salt.  Its  analysis  was  as  follows  : 


.2063  grams  lost  .0422  grams  upon  ignition  =  20.46% 
.2109  grams  lost  .0429  grams  upon  ignition  =  20.34% 
•2097  grams  lost  .0426  grams  upon  ignition  =  20.31% 


Mean  =  20.3?-% 


.2061  grams  gave  .1635  grams  mixed  oxide  =  79.33% 
.2039  grams  gave  .1621  grams  mixed  oxide  =  79.49% 
.2106  grams  gave  .1670  grams  mixed  oxide  =  79.29% 
.1982  grams  gave  .1573  grams  mixed  oxide  =  79.36% 


Mean  =  79-37% 


12 


.2043  grams  gave  .01 10  grams      g227 

.2079  grams  gave  .0113  grams  Mg2P2Ot  =  3.46%  P2O5 

.2013  grams  gave  .0106  grams  Mg2P2O7 

.2102  grams  gave  .0118  grams  Mg2P2C>7  =  3. 


Mean  =  346%  P2OS 

.2016  grams  gave  .0073  grams   (NH4)2O  =  3-62% 
.2097  grams  gave  .0073  grams   (NH4)2O 
.2056  grams  gave  .0071  grams   (NH4)2O  =  3.. 

Mean  =  3.52% 


MoOs  by  difference 75-91  % 

P2O5    3.46% 

(NH<)20    3-52% 

H.O  by  difference  16.84% 


Total     9973% 

The  formula  calculated  from  these  percentages  is, 
22  MoO3.  P2OS.  3(NH4)2O.  39  H2O. 


SALT  No.  7. 

On  returning  to  monosodium  phosphate,  in  this  instance 
24  g.  of  the  latter  dissolved  in  300  c.c.  of  water  were  boiled 
with  28.8  grams  of  molybdic  acid  dissolved  in  ammonium 
hydroxide.  The  excess  of  the  latter  being  expelled,  the 
complex  salt  precipitated  from  this  solution  in  nitric  acid 
gave  the  following  results  upon  analysis: 

.2116  grams  lost  .0433  grams  upon  ignition  =  20.46% 

.2072  grams  lost  .0433  grams  upon  ignition  =  20.27% 

•2057  grams  lost  .0419  grams  upon  ignition  =  20.37% 

.2093  grams  lost  .0428  grams  upon  ignition  =  20.45% 


Mean  =  20.39% 


13 

.2O27  grams  gave  .1612  grams  mixed  oxides  =  79.53% 
.2109  grams  gave  .1681  grams  mixed  oxides  =  79.71% 
.2043  grams  gave  .1628  grams  mixed  oxides  =  79.69% 
.2062  grams  gave  .1642  grams  mixed  oxides  =  79.63% 


Mean  =  79.64% 


.2019  grams  gave  .0114  grams  Mg2P2O7  = 
.2042  grams  gave  .01  10  grams  Mg3P2OT  =  343%  PzOs 
.2057  grams  gave  .0114  grams  MgsPzOi  =  3.52%  P2O8 
.2022  grams  gave  .0112  grams  Mg2P2O7  =  3.5i  P2O5 


Mean  =  3.52%  P2O5 

.2116  grams  gave  .0075  grams  (NH4)2O  =  3.54% 
.2076  grams  gave  .0072  grams  (NH4)2O  =  3.47% 
.2091  grams  gave  .0076  grams  (NH4)2O=:3.64% 
.2078  grams  gave  .0074  grams  (NH4)2O  = 


Mean  =  3.55% 

MoO3  by  difference 76.12% 

P2O5    3.52% 

(NH4)20    •    3-55% 

H2O  by  difference 16.84% 

These  corresponded  to  the  formula: 

21  Mo03.  P205.  3(NH4)20.  37  H2O. 

SALT  No.  8. 

This  was  obtained  from  28.4  grams  of  di-sodium  phos- 
phate and  28.8  grams  of  molybdic  acid.  Its  analysis  showed 
the  following  percentages : 

.2016  grams  lost  upon  ignition  .0413  grams  =  20.49% 
.2054  grams  lost  upon  ignition  .0418  grams  ==20.35% 
.2106  grams  lost  upon  ignition  .0432  grams  =  20.51% 
.2029  grams  lost  upon  ignition  .0414  grams  =  20.40% 

Mean  =  20.44% 


.2063  grams  gave  .1641  grams  of  mixed  oxides  =  79.54% 
.2039  grams  gave  .1619  grams  of  mixed  oxides  =  79.34% 
.2002  grams  gave  .1592  grams  of  mixed  oxides  =  79.52% 
.2091  grams  gave  .1662  grams  of  mixed  oxides  =  79.48% 


Mean  =  79.47% 


.2117  grams  gave  .0111  grams  Mg2P2C>T  =  3.35%  P2O5 
.2042  grams  gave  .0108  grams  MgaP2OT  =  3.38%  P2O8 
.2091  grams  gave  .0113  grams  Mg2P2Or  ==  3.44%  PaOs 
.2076  grams  gave  .0114  grams  MgaPaOt  =  3.52%  P2O5 


Mean  =  3.47% 

.2129  grams  gave  .0080  grams  (NH4)oO  =3.76% 
.2147  grams  gave  .0084  grams  (NH4)2O  =  3.9i% 
.2019  grams  gave  .0078  grams  (NH4)2O  =  3.86% 
.2056  grams  gave  .0077  grams  (NH4)  20  =  3.74% 

Mean  =  3.82% 


MoOs  by  difference 76.00% 

P208    ,3.47% 

(NH4)20 3.82% 

H2O  by  difference *  16.62% 

Total    99.91  % 


The  formula 

22  MoO3.  P2O5.  3(NH4)2O.  38  H2O 
is  readily  deduced  from  the  preceding  percentages. 


SALT  No.  9. 

This  compound  was  made  by  the  interaction  of  32.8 
grams  of  tri-sodium  phosphate  and  28.8  grams  of  molybdic 
acid.  Its  analysis  showed, 


15 

.2071  grams  lost  .0405  grams  upon  ignition  =  19.56% 
.2046  grams  lost  .0399  grams  upon  ignition  =  19.50% 
.2057  grams  lost  .0398  grams  upon  ignition  =  19.35% 
.2094  grams  lost  .0406  grams  upon  ignition  =  19.39% 


Mean  =  19.45% 

.2029  grams  gave  .1637  grams  mixed  oxides  =  80.68% 
.2163  grams  gave  .1747  grams  mixed  oxides  =  80.76% 
.2095  grams  gave  .1691  grams  mixed  oxides  =  80.72% 
.2083  grams  gave  .1683  grams  mixed  oxides  =  80.79% 

Mean  =  80.74% 

.2116  grams  gave  .0118  grams  MfePsOr  =  3-55%  P.Os 
.2149  grams  gave  .0119  grams  Mg2P2Oi  =  3.54%  PzOs 
.2016  grams  gave  .0109  grams  Mg2P3OT  =  3-42%  PaOs 
.2030  grams  gave  .01  n  grams  Mg»P»O»  =  3.50%  P2O5 


Mean  =  3.50%  P2O5 

.2052  grams  gave  .0079  grams  (NH4)  20  =  3.85% 
.2069  grams  gave  .0091  grams  (NH4)  2O  =  3-9i% 
.2007  grams  gave  .0079  grams  (NH4)2O  =  3-94% 
.2151  grams  gave  .0082  grams  (NH4)2O  = 


MoO3  by  difference =  77-24% 

P2O5 =  3-50% 

(NH4)2O    =  3-88% 

H,O  by  difference  =  15-57% 


Total    =  100.19% 

These  values  lead  to  the  formula, 

22  MoO3.  P2O».  3(NH4)2O.  36  H2O. 

SALT  No.  10. 

Return  was  made  again  to  the  mono-sodium  phosphate, 
12  grams  of  which  were  boiled  together  with  14.4  grams  of 


i6 


molybdic  acid.  In  the  analysis  of  the  product  it  was  con- 
cluded to  determine  only  the  molybdic  and  phosphoric  acid 
content. 

Analysis. 

.2072  grams  gave  .1655  grams  mixed  oxides  =  79.87% 
.2098  grams  gave  .1674  grams  mixed  oxides  =  79.79% 
.2032  grams  gave  .1624  grams  mixed  oxides  =  79.92% 
.2051  grams  gave  .1636  grams  mixed  oxides  =  79.77% 


Mean  =  79.84% 

.2069  grams  gave  .0121  grams  Mg2P2O7  =  3.72%  P.O5 

.2046  grams  gave  .0118  grams  Mg2P2C>7  =  3.67%  PaO8 

.2017  grams  gave  .0115  grams  Mg^Oi  =  3.62%  P2O5 

.2039  grams  gave  .0119  grams  Mg-jPaOi  =  3.73%  P2O5 


Mean  =  3.68%  P,O5 


MoO3 


....=76.16% 
....=   3.68% 


Here  the  ratio  of  molybdic  acid  to  phosphoric  acid  is 
as  20:  i. 

SALT  No.  n. 

In  its  preparation,  12  grams  of  m'ono-sodiu.m  phosphate 
and  21.6  grams  of  molybdic  acid  were  used,  that  is,  the 
latter  was  decidedly  in  excess.  The  salt  which  separated 
showed  the  following  acid  content  upon  analysis: 

.2055  grams  gave  .1528  grams  mixed  oxides  =.  79.22% 
.2154  grams  gave  .1703  grams  mixed  oxides  =  79.0670 
.2022  grams  gave  .1599  grams  mixed  oxides  =  79.08% 
.2235  grams  gave  .1772  grams  mixed  oxides  =.  79.27% 


.1813  grams  gave  .0112  grams  MgiFiOt  =3.92%  P2O5 
.2000  grams  gave  .0117  grams  MgaPsOt  =  3.75%  PjOe 
.2029  grams  gave  .0126  grams  MgtPaOr  =  3,94%  P£O3 

.2913  grams  gave  .0182  grams  Mg2P2O7  =  3.98%  P£OB 


Mean  =  3.90%  P2O5 


I? 

MoO3  by  difference  .......................  =  75-28% 

P,O5    .......................................    3-90% 

Here  the  ratio  of  molybdic  acid  to  phosphoric  acid  is 
19:1. 

SALT  No.  12. 

In  this  salt  the  quantity  of  mono-sodium  phosphate  con- 
tinued the  same  as  in  salts  n  and  10,  while  the  molybdic 
acid  content  was  increased  to  36  grams.  The  product  sub- 
mitted to  analysis  gave  these  percentages  : 

.2835  grams  gave  .2204  grams  mixed  oxides  =  77-74% 
.2211  grams  gave  .1721  grams  mixed  oxides  =  77-84% 
.2088  grams  gave  .1624  grams  mixed  oxides  =  77-77% 
.2439  grams  gave  .1899  grams  mixed  oxides  =  77.86% 
.2664  grams  gave  .2071  grams  mixed  oxides  =  77-74% 

Mean  =  77-79% 


.2084  grams  gave  .0135  grams  MgzPzOi  =  3.91% 
.2058  grams  gave  .0123  grams  Mg2P2O7  =  3-79%  P=Os 
.2065  grams  gave  .0127  grams  MgaP2O7  =  3.92%  P2O5 
.2217  grams  gave  .0142  grams  MgaPsOT  =  3-88%  P2O5 


Mean  =  3.87%  P2O5 

MoO3  by  difference =  73-92% 

P2O5    , =   3-87% 

Hence  the  ratio  of  molybdic  acid  to  phosphoric  acid 
was  again  19:  i. 

SALT  No.  13. 

The  quantity  of  molybdic  acid  in  this  instance  was  43 
grams,  while  that  of  mono-sodium  phosphate  remained  as 
before.  Upon  analysis  of  the  product  the  ratio  between  the 
two  acids  was  found  to  be  20:  I. 

SALT  No.  14. 

In  this  case  50  grams  of  molybdic  acid  was  treated  with 
12  grams  of  mono-sodium  phosphate.   From  the  six  analyses 
made  to  determine  the-acid  ratio  the  result  was 
19 :  i  of  MoOs  to  P2O0. 


i8 

SALT  No.  15. 

Continuing  as  before  to  increase  the  quantity  of 
molybdic  acid  while  continuing  the  preceding  amount  of 
mono-sodium  phosphate  the  analysis  of  the  product,  which 
was  repeated  six  times,  showed  the  acid  ratio  in  the  salt 
to  be 

18  MoO3 :  i  PsOn. 

SALT  No.  16. 

In  this  instance  the  same  idea  of  increasing  the  content 
of  molybdic  acid  was  preserved,  so  that  64.8  grams  of  this 
acid  were  boiled  together  with  10  grams  of  mono-sodium 
phosphate.  The  eight  analyses  made  to  determine  the  acid 
content  proved  that  the  ratio  of  these  was 

22  MoO3 :  i  PsOs. 

SALT  No.  17. 

Here  72  grams  of  molybdic  acid  and  12  grams  of  mono- 
sodium  phosphate  interacted.  On  analyzing  the  product  the 
ratio  of  molybdic  acid  to  phosphoric  acid  was  found  to  be 
as  18:  i. 

SALT  No.  18. 

In  making  this  salt  the  quantity  of  molybdic  acid 
equaled  108  grams,  with  12  grams  of  mono-sodium  phos- 
phate. The  analysis  of  the  resulting  product  showed  the 
acid  ratio  to  be 

19  MoO3 :  i  P2O5. 

SALT  No.  19. 

With  144  grams  of  molybdic  acid  and  12  grams  of 
mono-sodium  phosphate,  the  crystalline  complex  salt  showed 
the  acid  ratio  to  be 

19  MoO2 :  i  P2O6. 


SALT  No.  20. 

In  this  instance  24  grams  of  mono-sodium  phosphate 
and  14.4  grams  of  molybdic  acid  were  brought  together  in 
150  c.  c.  of  water.  They  were  boiled  for  some  time  and 
upon  the  addition  of  nitric  acid  the  usual  yellow  colored 
precipitate  separated  but  in  small  amount.  When  it  was 
analyzed  it  showed  an  acid  ratio  of 

i6MoO3:i  P2OB. 

Other  salts  were  prepared,  with,  however,  the  same 
varying  results.  If  the  experiences  recorded  in  the  pre- 
ceding paragraphs  be  tabulated,  they  would  appear  as 
follows : 


Salt  used                          Mols.  taken 

Mols.  found 

Salt                  MoOa             H2O 

MoOj      P208  (NH4)2OH20 

NaH2PO4  .1  mol.  wt..  .1    mol.  wt.  150  c.  c. 

22 

3 

II 

NaH2PO4  .1  mol.  wt.  .15  mol.  wt.  150  c.  c. 

19 

NaHaPO*  .1  mol.  wt.  .25  mol.  wt  150  c.c. 

19 

NaH2PO4  .1  mol.  wt.  .3    mol.  wt.  150  c.  c. 

2O 

NaH2PO4  .1  mol.  wt  .35  mol.  wt.  150  c.  c. 

19 

NaH2PO4  .1  mol.  wt.  .4    mol.  wt.  150  c.  c. 

18 

NaH2PO4  .1    mol.  wt.  .45  mol.  wt.  150  c.  c. 

22 

NaH2PO4  .1  mol.  wt...5    mol.  wt.  150  c.c. 

18 

NaH2PO4  .1  mol.  wt  .75  mol.  wt  150  c.  c. 

19 

NaH2PO4  .1  mol.  wt.  .1    mol.  wt.  150  c.  c. 

19 

NaH2PO4  .2  mol.  wt  ,2    mol.  wt.  150  c.  c. 

24 

3 

13 

NaH2PO4  .2  mol.  wt.  .2    mol.  wt  300  c.  c. 

21 

3 

37 

NaH2PO4  .1  mol.  wt  .1    mol.  wt  300  c.  c. 

2O 

Na2HPO4  .1  mol.  wt  .1    mol.  wt  150  c.  c. 

22 

3 

ii 

Na2HPO4  .2  mol.  wt  .2    mol.  wt.  150  c.  c. 

2O 

3 

13 

NaaHPCX  .2  mol.  wt.  .2    mol.  wt.  300  c.  c. 

22 

3 

38 

Na3PO4      .1  mol.  wt  .1    mol.  wt  150  c.c. 

24 

3 

13 

Na3PO4      .2  mol.  wt.  .2    mol.  wt.  150  c.  c. 

22 

3 

39 

Na3PO4      .2  mol.  wt  .2    mol.  wt.  300  c.  c. 

22 

3 

36 

An  inspection  of  these  results  would  show  that  six  of 
the  salts  that  have  been  analyzed  show  the  ratio  of  acids 
to  be 

22  MoO» :  i  PaOB ; 


20 

three  show  the  ratio 

20  MoOs :  i  PaO8 ; 

five  show  the  ratio  of 

: 

19  MoO3:  i  P2O8; 
two  show  respectively  the  ratio  of 

18  MoO3 :  i  P2OB, 

and 

24  MoO8 :  i  P2OB, 

while  one  salt  gave  the  ratio 

21  MoO3 :  i  P2O8, 

with  no  apparent  reason  for  the  variation.  Hundeschagen,7 
however,  has  proved  that  ammonium  phospho-molybdate 
prepared  in  the  usual  way  invariably  carried  with  it  two 
molecules  of  mineral  acid;  also  that  salts  dried  below  130° 
varied  greatly  in  composition,  and  not  until  they  were  dried 
above  that  temperature  was  the  composition  likely  to  be 
constant.  From  his  results  he  deduced  the  formula 

12  MoO3.  PO*.  (NH4)2O, 

thus  giving  an  entirely  new  ratio. 

While  the  results  of  my  investigation  do  not  conclu- 
sively demonstrate  the  exact  composition  of  ammonium 
phospho-molybdate,  it  is  evident  that  they  do  contribute  to 
the  idea  that  the  conditions  of  formation  largely  determine 
the  constitution  of  the  salt,  and  it  is  evident  that  to  get  a 
constant  ratio  for  the  acid  content  it  is  necessary  to  work 
under  very  definite  conditions  as  to  quantity  of  material 
present,  and  as  to  the  dilution  of  the  solution  in  which  the 
complex  salt  is  formed. 

'Fresenius'  Zeit.  fur  Analyt.  Chem.,  28, 141. 


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